ScienceShot

ScienceShot: Saturn's Auroras Decoded

The processes driving Saturn’s auroras are the same ones that generate the flickering displays in Earth’s skies, new research suggests. Although that’s what scientists had long suspected, until recently no instruments had been pointed at the ringed planet at just the right time to observe the phenomena in the detail required. The new data were gathered by sensors on the Hubble Space Telescope in April (upper left image) and May (the other five images) of 2013. When solar flares or other particularly strong bursts of charged particles slam into Saturn, lines in the planet’s magnetic field collapse, sending a cascade of particles into the planet’s atmosphere in polar regions. (Because Saturn’s atmosphere is largely composed of hydrogen, aurora emissions are mainly in the ultraviolet band of wavelengths.) The far ultraviolet images revealed that the front edges of the shimmering auroral curtains, which can stretch 1000 kilometers tall on Saturn, raced across the planet’s surface at more than 4 kilometers per second—about three times faster than the planet rotates, the researchers report in a forthcoming issue of Geophysical Research Letters. Trying to observe the details of Saturn’s auroras has essentially been a hit-and-miss proposal, the researchers say: The times at which solar flares strike the planet aren’t readily predictable, and until now the Hubble telescope hasn’t been looking at Saturn at the proper wavelengths just when a solar flare arrived.